linux-kernel - Re: [PATCH] Mention Intel Atom in Kconfig.cpu

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Message-ID: <20081013140228.GG29938@cs181140183.pp.htv.fi>
Date:	Mon, 13 Oct 2008 17:02:30 +0300
From:	Adrian Bunk <bunk@...nel.org>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Phil Endecott <phil_wueww_endecott@...zphil.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Mention Intel Atom in Kconfig.cpu

On Mon, Oct 13, 2008 at 09:30:14AM -0400, Arjan van de Ven wrote:
> On Mon, 13 Oct 2008 15:30:51 +0200
> Andi Kleen <andi@...stfloor.org> wrote:
> > 
> > > Core2 instruction set with tune=generic is still the best to set.
> > 
> > Not sure that is true. These option are mostly for the compiler.
> 
> exactly, and our benchmarks show that tune=generic is best right now
> for Atom. 
> (586 scheduling sounds nice, but the pipelines are rather different.
> And the benchmarks don't lie..  ;-)

That sounds a bit dangerous since tune=generic is documented to change 
the semantics between gcc versions to better fit more recent CPUs
(there's even a small difference between gcc 4.2 and gcc 4.3):

          As new processors are deployed in the marketplace, the
          behavior of this option will change.  Therefore, if you
          upgrade to a newer version of GCC, the code generated option
          will change to reflect the processors that were most common
          when that version of GCC was released.


cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
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